Paving Design: Is Rigid-Fix External Stone Paving the Way to Go?

Recent investigations into a number of paving failures in Australia have shown that very little is understood about the many aspects intrinsic to rigid-fix (stuck down) paving. This paper examines and documents some of the factors that can determine the success or failure of paving (assuming a high standard of workmanship). Additionally, it has become clear that most engineers who investigate paving failures fail to fully understand the complexities and interplay of the many factors. Such lack of knowledge leads to poor design, poor supervision, and ultimately poor performance. There are basically three types of paving systems—adhesive/mortar fix, sand-bedded, and setts/cobblestones in a soft mortar. All three systems are being used in Australia but there is undoubtedly an overriding rigid-fixing mentality. By fixing stone to a solid concrete base so that it cannot move is probably seen by most engineers and architects as the most straight-forward and most controllable solution. However, on analysis, it is a system that is subject to numerous potential lines of failure. Not only is there the nature of the stone itself such as the mineral composition, strengths, thermal characteristics, and porosity, but also the environment into which it is placed, the types of loading it is subject to, and how it is fixed. Stability of the base (including shrinkage), expansion/construction joints, size, thickness and shape of the pavers, the laying pattern, type of adhesive, thermal conditions at the time of fixing, influence of salts and water, and sealing, all play a significant role in determining the success or otherwise of rigid-fix paving.